POWER OUTAGE: Alex Rodriguez, who grounded into a rally-killing double play in the Yankees’ 10-5 loss to the Braves yesterday, has just six doubles this season. Photo: N.Y. Post: Charles Wenzelberg

Concerns have intensified about Alex Rodriguez because he is not hitting the ball over the wall enough.

But what is more disturbing is that he is not even hitting the wall — on a fly or a bounce.

He hit his 11th homer Wednesday, a classic Yankee Stadium blow that barely reached the short porch. That puts him on pace for 26 this year. Not up to his career standards. But hardly horrible.

But what do we make of this — Rodriguez has just six doubles? That’s right, six — just one in the last month. Yankees hitting coach Kevin Long termed that number “alarming.” Rodriguez said he has no explanation for why he is not hitting with enough authority to, at the least, drive some balls into the gap.

Both men insist Rodriguez’s approach is much better these days. He is seeing the ball well enough to be second on the team in walks and — more important — he shortened his leg kick a few weeks back and believes that has led to better swings, which, ultimately, will lead to more solid contact and plenty of extra-base hits of all types.

Nevertheless, this promise of better stuff in the offing has been going on for quite a while now without corresponding results. Instead, the troubling trend line persists as Rodriguez’s OPS has fallen each season from 1.067 in 2006 to .965 to .933 to .847 to .823 to .780 this year.

“There is a big gap between where he should be and where he is right now,” Long said. “What is hard is that I feel good about where his swing is. He is not lost. I do feel a good streak is coming.”

For now, though, Rodriguez’s six doubles are 16 fewer than cross-town third baseman David Wright and ranks 234th in the majors. This from a man who is 54th all time in doubles at 501 and seventh among active players.

A-Rod is first among active players with 1,170 extra-base hits and 10th all-time, yet even with yesterday’s homer he has just 17 extra-base hits, which is tied for 137th in the majors.

Long theorized that Rodriguez has missed out on a few doubles because “he has lost some speed out of the box.” Nevertheless, those types of doubles typically are the ones that split outfielders, but don’t reach the wall and, thus, are about placement, hustle and quickness. Let’s say Rodriguez has lost even three doubles that way. That gets him to nine. Still not impressive, and we still are wondering where the no-doubters are that go for stand-up doubles.

“As it stands now, those are alarming numbers,” Long said. “Those numbers have to improve — and I think they will.”

Rodriguez said, “I just know that I am getting closer. I know the at-bats are getting better and after that I am sure the numbers will jump.”

But how high? Long, perhaps the biggest A-Rod supporter, said, “He’s a 30-homer guy now, 40 is farfetched. Realistically, 30 is the number to shoot for.”

Look, we know the theories. Rodriguez turns 37 next month, and his body has been beaten up. Since admitting to using steroids in spring 2009, Rodriguez has failed to revive the sustained genius of his prime. Now, it was not long ago that age had us wondering if Derek Jeter still could deliver prolonged success and, since last July, he has performed near his career standards. And Jeter turns 38 next week.

So maybe A-Rod still can muster that. Long insists Rodriguez continues to put on homer displays in batting practice.

“I know it is just a glimpse now, but I have seen enough that I know we are going to get more than just a glimpse,” he said. “We are going to get something special that lasts two months.”

Yesterday, Rodriguez gave a glimpse with a homer, but then grounded into a double play with the tying run on third and one out in the seventh. The Yankees lost 10-5. Rodriguez is hitting .215 this month with one double.

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QUIZ: Name the top five in doubles among active players (answer below).

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Melky’s turned the corner

On Tuesday, Melky Cabrera overtook Ryan Braun to gain third place in voting among outfielders for the NL All-Star team and then overtook Willie Mays to become the fastest San Francisco Giant to 100 hits in a season. He needed 291 at-bats. Mays needed 295 in 1958.

He went into his game last night against the Angels with 101 hits and an MLB-best 302 — 10 more than anyone else — since the beginning of last season. Cabrera was hitting .369 this year with a .945 OPS, moving Long to say, “He’s a hell of a player. He has totally gotten committed to his career. He doesn’t drink. He doesn’t take anything for granted any more. His personal trainer is with him all the time. When you go all in and have talent, this is what happens — and it is evident he has the talent.”

Long said it was clear Cabrera had talent before he was traded to Atlanta, but was “pudgy” and not as diligent about his career.

“If Melky committed himself to the Yankees as he does now, he would still be a Yankee,” he said. “And he would say the same thing. He made himself tradeable then.”

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Cashman: Nunez a shortstop

On the subject of the Yankees and left field, I continue to think Eduardo Nunez would be best served moving to that position and away from his high-error infield ways. I recognize I am probably a bigger fan of Nunez than most, believing if he played regularly he would hit good pitching with 15-homer power while also providing high-end speed.

But when I asked about this move recently, Yankees general manager Brian Cashman could not have been more emphatic in disagreeing.

Cashman said he sees Brett Gardner as an above-average asset in left because of his on-base skills, speed and elite defense.

“I think he is a shortstop,” Cashman said of Nunez. “He can play the outfield, but he does not profile as an outfield guy. He is a free swinger and his defense would not be a plus. Put his OPS in left field and I think it would rank near the bottom.”

For now, Nunez — like Gardner — continues not to play. He has been out since May 19 with a thumb injury.